The aim of this project i to increase the basic understanding of how innate behavior patterns (i.e. "fixed action patterns") and recognition mechanisms (i.e. "innate releasing mechanisms") are coded in and controlled by the nervous system. For this purpose, anuran (toads and frogs) acoustic behavior, i.e. calling and responding to calls, is being studied. This behavior is especially appropriate because of its relative simplicity, the species- specificity of some calls, and the fact that some calls can be elicited in essentially normal form by brain stimulation in restrained animals. Anurans are especially appropriate because of their high tolerance of radical surgical procedures, accessibility and simplicty of their nervous systems, and ready availability and maintenance. Movements during calling are studied by applying such techniques as electromyographic recording from various muscles, observation of the larynx through a transparent eye plug fixed in an enucleated orbit, and cinematography of the larynx. Study of the neural mechanisms of acoustic behavior involves the production of brain lesions, electrical stimulation of the brain, and recording of neural activity from the brain. Neurohistological methods are used to define lesions and electrode positions and to study the basic neuroanatomy of the brain areas involved in acoustic behavior. An especially important technique has just been developed and will be used extensively. This involves the recording of neural correlates of calling from the partially or completely denervated brain stem during electrically-evoked calling. In this method, calling behavior is represented by the electromyograms of just two laryngeal muscles.